By now you’ve probably heard that there are over 1,800 billionaires roaming around and that Bill Gates is the richest man on Earth with well over $79 billion. But did you know that the chances of you becoming a millionaire are quite likely 100 percent? Didn’t think so.

Although the chances of most of us becoming billionaires—let alone multi-billionaires— is hugely tiny. On the other hand, becoming a millionaire is like oh-so attainable that it usually doesn’t even cross our minds. Here’s the math to prove it:

Take out a pencil and paper, or if you must, tap the calculator app on your phone or find a calculator on your computer. Then plug in two sets of numbers. Both will be estimates. The first figure will be the number of years you intend to work. For example, if you work from age 25 to 65, that would be 40 years. The second figure will be an estimate of how much you think your salary will average over those years. Let’s pretend that’s $50,000.

Multiple the number of years, 40, by the annual salary, $50,000, and viola, the result shows that you would earn $2 million dollars. And that makes you not just a millionaire but also a multi-millionaire.

In reality, how much of that $2 million is actually take home pay depends upon a number of variables including taxes, FICA, savings contributions, etc., but nonetheless, the whole sum gives you multi-millionaire status.

Even using an average annual income of $20,000 for 40 years, totals $800,000 over that lifetime of work and is a figure of substance large enough to make one feel good about their earning power even though it’s not enough to live on. A living wage, however, is a subject for another day.

Knowing that seven-figure tallied incomes are coming your way is one thing, investing to earn millions is another. But no worries, the math in figuring out how to do that is simple, too.

By using the Rule of 72 you can find out how many years it will take for money to double in value. To do so divide 72 by a figure representing an interest rate. For instance, assume the average return on stocks in the market is 8 percent, and it will take 9 years for money to double. That means $10,000 will grow to $20,000 in nine years.

The compounding of money over time has been referred to as the Eighth Wonder of the World and nowhere is that clearer than when we are trying to see how money grows over time Here are a few particulars:A one-time lump sum investment of $10,000 earning a consistent 4 percent a year and invested for 10 years will grow to $14,802. Allow that money to work for 30 years and you’ll have $32,434; and in 50 years, $71,067.

An 8 percent return means $10,000 will grow to $217,245 in 40 years and nearly $470,000 in 50 years. Bump that return up to average 12 percent a year and in 30 years those investment dollars will have grown to around $300,000 and in 50 years, $2,890.022, according to About.com.

Given that a 12 percent average return for decades is pretty hard to imagine these days, let’s stick with more realistic returns, such as those in the 4-8 percent range. And then plan accordingly understanding all the while that Millionaire Land is closer than you think —provided you work—and save—for it.